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Thursday, January 9, 2014

In December 1953, color television
broadcasts were first approved by the U.S. Federal Communications
Commission. Soon thereafter, the first color television sets went on
sale for the bargain price of more than US $1,000 (present day: US $7,850). Journal of Sedimentary Petrology readers
found a way to break free and read a paper by Werner Bruckner that examined links between cyclic strata and
climate change—a topic still of considerable interest today. Bruckner offered
numerous insights, including the now-classic line, “When a detailed study of limestones is made, their interpretation
becomes more difficult.” Overcoming the challenges, he proposed a
conceptual model wherein climatic oscillations (changes in temperature)
influenced the saturation state of calcium carbonate, which led to cyclicity. He
further proposed that the utility could include “correlating formations and
climatic events over distances of continental size.”

Monday, January 6, 2014

Sediments record the
mechanisms of transport and deposition, but the details of the precision and
accuracy of interpretations of processes from the preserved record remains
ambiguous. To explore this concept in a fluvial system, Draut and Rubin analyzed relations between grain-size progression
in suspended sediment and flood deposits from controlled, dam-release
floods in the Colorado River through Marble-Grand Canyon. The results revealed that for these simple
floods, most deposits show inverse grading that reflects coarsening suspended
sediment (a result of fine-sediment-supply limitation). But eddy-scale variability
creates some profiles with normal grading, a pattern that does not reflect
grain-size evolution in the flow as a whole. The results are interpreted to
suggest that systemwide grain-size evolution in modern or ancient depositional
systems requires sampling enough deposit profiles that the standard error of
the mean of grain-size-change measurements becomes small relative to the
magnitude of observed changes. Collectively, the results reveal that, with
sufficient sampling, fluvial deposits can faithfully reveal paleo-sediment flux
and discharge.